Recommendations for the Care of
Amphibians and Reptiles in Academic
Institutions
F. Harvey Pough
NATIONAL ACADEMY PRESS
Washington, D.C. 1992
Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . .S5
Amphibians and Reptiles in Research and Teaching . . . . .S5
The Biology of Amphibians and Reptiles . . . . . . . . . .S6
General Recommendations for the Care of Ectothermal VertebratesS8
The Physical Environment. . . . . . . . . . . . . . .S8
The Biological Environment. . . . . . . . . . . . . S11
Marking Individuals. . . . . . . . . . . . . . . . . . . S15
Breeding . . . . . . . . . . . . . . . . . . . . . . . . S15
Environmental Conditions and Medical Care. . . . . . . . S17
Health Precautions for Release of Animals. . . . . . . . S17
Health Precautions for Animal Caretakers . . . . . . . . S17
Summary. . . . . . . . . . . . . . . . . . . . . . . . . S18
Acknowledgements . . . . . . . . . . . . . . . . . . . . S18
References . . . . . . . . . . . . . . . . . . . . . . . S18 Recommendations for the Care of Amphibians and Reptiles
in Academic Institutions
F. Harvey Pough
Dr. F. Harvey Pough, Ph.D, is professor of Ecology and
Systematics and director of the Laboratory of Functional
Ecology at Cornell University in Ithaca, New York.
INTRODUCTION
Amphibians and reptiles differ in many respects from the mammals and birds most
commonly used in biomedical research. These differences affect the physical and biological
requirements of amphibians and reptiles in captivity. In this contribution, some basic
biological characteristics of these animals are described that are relevant to their husbandry.
My goal is to help members of institutional animal care and use committees appreciate the
requirements of amphibians and reptiles in captivity, and to make suggestions that will be
helpful in designing housing and providing day■to■day care.
I will focus on amphibians and reptiles used for research and teaching in colleges and
universities. In the sense that amphibians and reptiles are exotic animals in a biomedical
context, there are parallels between their use in academic settings and in zoos and aquariums.
However, the facilities and resources available at colleges and universities are more limited
than those of most zoos and aquariums. These recommendations address the limitations and
opportunities of small■scale husbandry.
The husbandry practices suggested here are compatible with the Health Extension Act
(PL■99■158), with the National Research Council's Guide for the Care and Use of
Laboratory Animals (NRC, 1985) with the Canadian Council on Animal Care's Guide to the
Care and Use of Experimental Animals (Canadian Council on Animal Care, 1980) and with
the Guidelines for Use of Live Amphibians and Reptiles in Field Research (American Society
of Ichthyologists and Herpetologists et al., 1987).
AMPHIBIANS AND REPTILES IN RESEARCH AND TEACHING
Understanding the husbandry requirements of amphibians and reptiles begins with
understanding why these animals, rather than traditional biomedical species, are being
studied. Studies of amphibians and reptiles often have different perspectives and goals than
those using traditional biomedical species. These differences are reflected in the housing and
care that is appropriate for the animals. In addition, the physical and biological needs of
amphibians and reptiles differ from those of mammals and birds, and are often more difficult
to provide in an artificial setting. Both of these factors must be appreciated by investigators
working with these animals, and by the individuals responsible for evaluating protocols and
husbandry practices.
The Context of Study
Many studies of amphibians and reptiles have an organismal perspective. That is, the focus
of study is the intact animal and the context is the species as it functions in its natural
environment. This approach differs from the traditional biomedical use of mammals and
birds to illustrate general biological phenomena or to serve as models of specific human
diseases or genetic defects. In organismal research, behavior, ecology, physiology, and
morphology are studied in the context of phylogenetic relationships and environmental
specializations. Husbandry must consider the entire biology of an organism so that normal
behavior, physiological response, and morphogenesis can be assured.Much research in
organismal biology is currently directed to comparative studies that investigate the evolution
of physiological, morphological, and behavioral characteristics by studying a series of species
(see Brooks and McLennan, 1991; Harvey and Pagel, 1991; and Huey, 1987 for examples of
this approach). Studies of this sort rely upon measuring the same phenomenon (e.g.,
thermoregulation, parental care, or feeding mechanics) in several species. Reviewers of
protocols must understand that the study of multiple species of known phylogenetic
relationship is an essential element of the comparative approach, and is not duplication in the
sense prohibited by National Institutes of Health regulations.
Practical Considerations
Providing environments suitable for amphibians and reptiles can be difficult. Domestic
animals used in biomedical research have been bred to prosper under conditions that can
easily be maintained in an animal room. Amphibians and reptiles, on the other hand, are
wild animals, and the husbandry methods applied to them must take this into account.
Housing, food, and care must match the physical and behavioral needs of each species.
Carefully designed physical and biological environments are often needed, especially when
the goal of husbandry is to facilitate studies of complex responses such as hormonal cycles,
reproductive and social behavior, or water and temperature regulation. The welfare of the
animals must have the highest priority in the design of animal rooms, cages, and cage
furnishings. This effort must not be frustrated by the application of inappropriate standards
based on domestic species.
Because most species of amphibians and reptiles are not available on short notice or
from commercial breeding colonies, they are usually either collected from the wild by the
investigators themselves, or obtained by gift from other researchers, from zoos, or from
agencies such as the U.S. Fish and Wildlife Service. The availability of a species is likely to
be affected by its seasonal activity cycle, the opportunity to collect in an exotic locality, and
the provisions of national laws and international treaties. An investigator who plans to travel
thousands of miles cannot predict in advance exactly how many individuals of which species
will be collected.As a consequence of this uncertainty, investigators may have to submit
protocols that include several taxa, only a few of which will actually be used. Furthermore,
unusual species that have been successfully acclimated to laboratory conditions have a
scientific value that transcends the project for which they were originally collected, and they
may be kept indefinitely in expectation of further use. Animal care and use committees must
understand these practical aspects of working with amphibians and reptiles and evaluate
protocols accordingly.
THE BIOLOGY OF AMPHIBIANS AND REPTILES
In order to design appropriate environments for amphibians and reptiles, one must have an
appreciation for their unique biological characteristics. Some practices and materials that are
suitable and desirable for the care of birds and mammals are unimportant or even deleterious
for amphibians and reptiles. Conversely, considerations that have little relevance for birds
and mammals can be crucial for successful husbandry of amphibians and reptiles. A large
literature shows that husbandry practices that are appropriate for mammals are not suitable
for amphibians and reptiles, but the pertinent references are scattered. Recent sources of
general information about amphibians and reptiles include Bellairs (1969), National Academy
of Sciences (1974), Harless and Morlock (1979), Stewart (1984a,b), Duellman and Trueb
(1986), Halliday and Adler (1986), Seigel et al. (1987), Norris and Jones (1987), and Pough
et al. (1989) and the references therein.
Distinctive Characteristics
Two attributes of amphibians and reptiles underlie all aspects of their care: Ectothermy and
diversity.
Ectothermy. Amphibians and reptiles are ectotherms, that is, they do not ordinarily
generate enough metabolic heat to raise their body temperatures above the ambient
temperature. However, ectotherms are not literally "cold blooded." Under normal
conditions, terrestrial ectotherms regulate body temperature by behavioral means, often at
high levels and within narrow limits. Several important implications for their care follow
from this aspect of their biology. Most importantly, environmental conditions are quite
different from those appropriate for birds and mammals.
Ectothermy is an energy efficient mode of thermoregulation because metabolic energy
is not used to warm the body. As a result, the resting metabolic rates, aerobic capacities,
and overall energy needs of ectotherms are nearly an order of magnitude lower than those of
endotherms (birds and mammals) of similar size (Figure 1).
The thermoregulatory mechanisms employed by amphibians and reptiles are by no
means simple. Many ectotherms regulate their body temperatures during activity at levels
that are similar to those of birds and mammals (35■C to 42■C). The regulated temperature
may change in response to internal and external conditions. Changes in thermoregulatory
behavior include differences between daytime and nighttime temperature, elevation of body
temperature following feeding, an increase or decrease in body temperature during
pregnancy, a behavioral fever mediated by prostaglandin release during bacterial infection,
and muscular thermogenesis during egg brooding (Hutchison et al., 1966; Regal, 1966,
1967; Lillywhite et al., 1973; Vaughn et al., 1974; Van Mierop and Barnard, 1976, 1978;
Kluger, 1977, 1979; Hutchison and Erskine, 1981; Bartholomew, 1982; Beuchat, 1986;
Sievert, 1989). Humane care of amphibians and reptiles requires conditions that facilitate
their complex thermoregulatory responses.
Diversity. Living ectothermal tetrapods include nearly 4,000 species of amphibians and
6,000 species of reptiles, encompassing nearly 10,000 species of animals that display an
enormous array of lifestyles. This diversity makes these animals attractive for research at
the cellular or molecular level, as well as for studying organismal, ecological, and
evolutionary questions (Deuchar, 1975; Greenberg et al., 1989; Pough, 1989; Elinson et al.,
1990). For example, an investigator studying hormonal control of reproductive behavior can
choose from some 3500 species of anurans (frogs and toads). Among these are species that
retain an ancestral amphibian life cycle (terrestrial adults, aquatic eggs, and aquatic larvae);
terrestrial species in which either males or females carry developing eggs and/or young on
the back, in vocal pouches, and even in the stomach; species in which females feed their
tadpoles unfertilized eggs; and species that give birth to live young, either with or without
some form of matrotrophic contribution to the fetus. Moreover, anurans run the gamut from
totally aquatic frogs to species that live in deserts. Reptiles show still greater diversity in
habitats and specializations. Because the ecological characteristics and husbandry
requirements of the animals are so diverse, it is impossible to formulate specific guidelines
for groups larger than a few species. In fact, broad application of specific guidelines would
inhibit rather than promote humane care.
Sources of Information
The husbandry requirements of amphibians and reptiles in an academic setting are similar to
those in zoos and aquariums (Gans and Van den Sande, 1976; Gans, 1979; Murphy and
Campbell, 1987; Murphy and Chiszar, 1989), and research in zoos has been a fruitful source
of information about amphibians and reptiles (Sajdak, 1983). Publications for herpetological
hobbyists often provide useful guides for care of ectothermal vertebrates (e.g., Mattison,
1982, 1988; Obst et al., 1988; de Vosjoli, 1989, 1990). Journals like Lacerta, Reptile &
Amphibian Magazine, Salamandra, and Vivarium). Herpetological Review, published by the
Society for the Study of Amphibians and Reptiles, has a section on "Herpetological
Husbandry." The International Zoo Yearbook usually contains sections about amphibians
and reptiles, and much of Volume 28 (1989) of this series was devoted to their care.
Symposia, newsletters, and special publications of herpetological societies are also helpful
sources of information (e.g., Bowler, 1977; Murphy and Armstrong, 1978; Ferner, 1979;
Murphy and Collins, 1980; Gray and Bumgardner, 1984; Gray, 1985; Gowen, 1987, 1989;
and the Bulletin of the Association of Amphibian and Reptilian Veterinarians). The
professional staff at zoos and aquariums can often provide advice about the husbandry
requirements of a particular species. Such advice may be particularly helpful in establishing
breeding programs. Slavens (1989) publishes an annually■updated inventory of reptiles and
amphibians in zoos and private collections; this volume can lead to an appropriate source of
information about a particular species.
The diversity exhibited by amphibians and reptiles presents problems for husbandry
that are not encountered with domestic and laboratory birds and mammals. Husbandry
conditions must match the needs of the species being kept. Three factors are essential to
achieve that goal:
1. Knowledge of the natural history of each species, obtained from field observations
or from the literature;
2. Duplication of the features of the animals' natural microhabitats that are crucial for
normal behavior and physiological function; and
3. Awareness and sensitivity on the part of caretakers to the unique requirements of
these animals and the ways in which they manifest ill■health.
GENERAL RECOMMENDATIONS FOR THE CARE OF ECTOTHERMAL
VERTEBRATES
The following generalizations apply to the care of most amphibians and reptiles, but caution
must be employed in their use. The taxonomic categories included are broad, and substantial
variation exists within them. Some lizards, for example, are heliothermic and regulate their
body temperatures between 38 and 42■C, whereas others live beneath the canopies of tropical
forests with body temperatures that fluctuate between 25 and 30■C. Still others are nocturnal
and active at body temperatures below 20■C. Similarly, some amphibians are entirely
aquatic, whereas others may never see a body of water larger than a pool of rain drops on a
leaf. While these guidelines emphasize the factors that are likely to be important for
husbandry and point to general categories of problems and solutions, information about the
ecology and physiology of the species being kept is indispensable.
The Physical Environment
Housing conditions must provide appropriate temperature, moisture, and light regimes. In
general, these include visible and ultraviolet light controlled on a daily and seasonal cycle,
water for drinking or bathing, and high relative humidity. High rates of air flow are not
usually required in animal rooms housing amphibians and reptiles. Limiting the number of
air changes per hour greatly simplifies the task of maintaining high humidities. In most
cases the key to successful care of amphibians and reptiles lies in providing a gradient of
conditions within the cage that allowing animals to combinations of environmental factors
needed.
Temperature. The thermoregulatory requirements of amphibians and reptiles are different
from those of birds and mammals and are more difficult to satisfy in captivity. As
endotherms, birds and mammals have continuously high rates of metabolic heat production,
and thermoregulation consists primarily of adjusting the insulating value of hair or feathers to
equalize the rates of heat production and loss. Endotherms accomplish this regulation over a
broad range of air temperatures. The radiative environments of the animal room and their
cages normally have little significance.
In contrast, amphibians and reptiles balance heat uptake from the environment (Tracy,
1976, 1982) with heat loss to the environment. Control of the radiant environment of the
cage (in both the infrared and visible wavelengths) is especially important, because this is
usually the major pathway of heat gain and loss. The thermoregulatory behaviors of many
species, especially reptiles, are based on adjusting position, posture, and reflectivity in
response to radiant flux. These animals may be unable to respond appropriately to a uniform
temperature or to a substrate temperature gradient. Lizards can be confused by unnatural
combinations of temperature and light intensity. For example, lizards controlled their body
temperatures more effectively in gradients that provided the normal stimulus of bright light
and heat at the same end of the gradient than they did in gradients that were uniformly
lighted or those that combined bright light with low temperatures (Sievert and Hutchison,
1991). Photothermal gradients employing incandescent bulbs that produce both heat
and light are probably the best choice for long■term care (Regal, 1980). These gradients
must provide cool retreat sites as well as warm basking spots for the animals. Because the
body temperatures that many species of lizards maintain during activity are only a few
degrees below their lethal temperatures, overheating is a substantial risk if gradients are
poorly designed. The cage must be large enough so that one end always remains cool, and
cages that incorporate photothermal gradients should never be covered with solid lids that
prevent the escape of heat. Shelters should be placed along the length of the gradient so that
animals are not forced to choose between thermoregulation and security. In most cases, a
variable temperature regime is necessary (Regal, 1967, 1971). Animals kept continuously at
the warm body temperatures they select voluntarily during activity may show deleterious
physiological changes (Licht, 1965). Transient exposure to high temperatures may suppress
the immune system of reptiles (Elliott Jacobson, personal communication).
Choosing the range of temperatures that should be provided for a particular species
requires information about its phylogenetic affinities and ecology. The thermoregulatory
characteristics of groups of reptiles have been summarized (Avery, 1982). In particular,
Ford (in press) suggests appropriate temperatures for snakes. In general, amphibians are less
heliothermic than reptiles, and the high rate of evaporative water loss characteristic of
amphibian skin counteracts radiant heat uptake (Lillywhite, 1975; Tracy, 1976).
Nonetheless, adult and larval amphibians bask in the sun or use temperature gradients to
regulate body temperatures. A thermophilic response after feeding and behavioral fever
mediated by prostaglandin A1 have been reported for amphibians (Lillywhite et al., 1973;
Hutchison and Erskine, 1981). Substrate temperature gradients produced by heating elements
beneath the cage floor may be more effective than photothermal gradients, especially for
nocturnal or secretive amphibians. The thermoregulatory characteristics of amphibians have
been summarized (Brattstrom, 1979; Hutchison, in press), and information about salamanders
can be found in Feder et al. (1982) and the references therein.
Water. A shallow container of water is appropriate for many amphibians and reptiles.
However, some tropical species require daily spraying, and some desert reptiles never drink.
Amphibians do not drink; terrestrial species absorb water through the skin and anurans have
an area of skin in the pelvic region that is specialized for this function. Shallow water
dishes, moist substrates, and spraying are appropriate for terrestrial amphibians. Chlorinated
water should be avoided, especially for aquatic amphibians, and water bowls should be
changed as often as practical because Pseudomonas populations increase rapidly in stagnant
water (Elliott Jacobson, personal communication).
Humidity and Air Flow. Most amphibians and reptiles are much smaller than laboratory
mice (Pough, 1980, 1983). An adult white mouse weighs about 20 g, while nearly 80
percent of the species of lizards and frogs and 95 percent of the salamanders have adult body
masses smaller than 20 g (Figure 2). Indeed, 8 percent of lizards, 17 percent of frogs, and
20 percent of salamanders weigh less than 1 g as adults! These very small body sizes have
important implications for husbandry (Pough, in press). In their natural environments, most
amphibians and reptiles spend their time at the ground surface, under leaf litter, or in
burrows. As a result they are exposed to microclimates (especially humidities and rates of
air movement) that are very different from those perceived by large animals like humans.
Even desert species spend much of their time in burrows or buried in loose sand. Relative
humidity approaches saturation in these microhabitats, and the low humidities characteristic
of heated and air■conditioned buildings can be stressful even for desert reptiles. Relative
humidities should be maintained above 70 percent (preferably at 80 percent) for nearly all
species of amphibians and reptiles. However, most reptiles develop skin lesions when they
are kept on wet substrates for long periods.
Amphibians can often be kept in cages with lids to keep humidity high, but many
reptiles require photothermal gradients. Putting a lid over a photothermal gradient quickly
leads to lethal overheating of the animals inside. Instead, it is necessary to maintain high
relative humidity in the entire animal room. Room air flow can be limited to a maximum of
one or two changes per hour to maintain the humidities these animals require.
The large number of incandescent lights required in a room that houses 20 or 30
cages of lizards or snakes may produce more heat than the air■handling system can exhaust,
especially when the number of air changes per hour is restricted to keep the relative humidity
high. It is wise to incorporate thermostats to turn off the lights when room temperature
approaches a level that is stressful for the least heat■tolerant species.
Light. Quality and quantity of light may both be important to amphibians and reptiles. An
annual cycle of day length is usually critical, especially for breeding colonies. Windows or
skylights that admit bright sunlight without overheating the room are ideal, but are rarely
included in animal rooms. In lieu of natural daylight cycles, timers can be used to control
photoperiod on an annual cycle.
The wavelengths of light provided to captive amphibians and reptiles also require
attention, but little is known about the effects of different light intensities and of varying
ratios of wavelengths. A trial■and■error approach has been adopted by zoos and individuals
who maintain these animals, however this body of anecdote constitutes nearly all the
information currently available.
Providing the proper amount and quality of ultraviolet light is probably the most
difficult aspect of lighting. Some species of amphibians and reptiles appear to require
ultraviolet light for calcium metabolism, normal behavior, and reproduction (Cole and
Townsend, 1977; Laszlo, 1969; Moehn, 1974; Townsend, 1979; Townsend and Cole, 1985;
Regal, 1980). Middle■wavelength ultraviolet light (UVB) penetrates the epidermis and
converts provitamin D3 to previtamin D3. Synthesis of the active form of the vitamin
(1,25■dihydroxyvitamin D3) by birds and mammals has been studied, but the process is not
well understood for amphibians and reptiles, some of which have as many as six types of
provitamin D3 in their skins (Holick, 1989a).
Some diurnal reptiles from open habitats have layers of melanin in the skin that block
penetration of ultraviolet light (Porter, 1967). These animals might require higher intensities
of light than do species with more translucent skins. Preliminary information from work at
the National Zoo suggests that green iguanas (Iguana iguana) cannot use dietary vitamin D3,
and must receive ultraviolet light for maintenance of blood levels of 1,25■dihydroxyvitamin
D3 (Mary Allen, personal communication). Similarly, birds and mammals synthesize two
types of vitamin D3, and dietary 1,25■dihydroxyvitamin D3 would not substitute for
cutaneous synthesis of 24■dehydrovitamin D3 (Holick, 1989b). However, several species of
lizards have been raised successfully without ultraviolet light, in some cases for two or more
generations, using dietary supplementation to provide vitamin D3 (Larry Talent, personal
communication; Gehrmann et al., 1991).
We do not know exactly what wavelengths of light are required for vitamin D3
synthesis by amphibians and reptiles, nor do we know whether the ratio of
middle■wavelength (290 to 315 nm) to long■wavelength (315 to 400 nm) ultraviolet light
(UVA) is important. Gehrmann (1987) presented information about the spectra of several
bulbs used in animal husbandry. Broad■spectrum fluorescent bulbs such as Vita■Lite■
(Duro■test) and Chroma 50■ (General Electric) may be effective (Regal, 1980), although
these lights, especially the Chroma 50 bulb, emit little energy in the middle■wavelength
ultraviolet portion of the spectrum. (Note that, contrary to common misconception among
hobbyists, Gro■Lux■ bulbs do not emit much ultraviolet light, and they are not appropriate
for UV supplementation, although they may be used in displays to support plant growth
without harm to animals) (Roberts and Gehrmann, 1990). Fluorescent BL (black light) bulbs
provide long■wavelength ultraviolet light (UVA). Bulbs designated BLB (blacklight blue)
have a filter that passes only ultraviolet wavelengths; they are more expensive than BL bulbs,
but no more effective for animal husbandry. Neither a twelve■hour daily exposure to
Vita■Lite■ nor a half■hour exposure to a Sylvania BL bulb was sufficient for normal
calcification of young chickens (Bernard et al., 1989), and the authors recommended that
these bulbs not be used for captive animals.
Middle■wavelength ultraviolet light (UVB) is provided by fluorescent sunlamp bulbs
of the sort sometimes used in treating psoriasis. In addition to the familiar tubular
fluorescent sunlamps, self■ballasted reflector mushroom■type mercury lamps emit UVA and
UVB radiation (William H. Gehrmann, personal communication). They are manufactured in
160 and 250 watt sizes by Philips Lighting Co. and Iwaski Electric Co. National Biological
Corporation (1532 Enterprise Parkway, Twinsburg, OH 44087) is a source of UVA and
UVB bulbs. Middle■wavelength ultraviolet light can injure the eyes of animals and
caretakers, and precautions should be taken to limit exposure. Species of reptiles differ
substantially in the UV exposure they require (Townsend and Cole, 1985; Gehrmann, 1987),
and a conservative approach is advised. Exposure periods of 30■45 minutes at a distance of
50 cm from a UVB lamp may be satisfactory for reptiles from open habitats (Moyle, 1989).
UV irradiance at the midpoint of tubular bulbs is about twice as intense as irradiance at the
ends (Gerhmann, 1987). Breaking the daily UVB exposure into 10■15 minute periods at
hourly intervals may help to ensure that all the individuals in a community cage have access
to the light.
Snakes may normally satisfy their vitamin D3 requirements from their diet of whole
animals (Ford, in press). Reptiles from forests, and amphibians in general, are probably
more sensitive to UV light than are desert reptiles, and UVB bulbs are probably not
appropriate for these animals. Early signs of UVB toxicity include failure to eat, lethargy,
diminished activity, and a gray or smokey skin color that turns progressively darker (William
Gerhmann, personal communication). All of these symptoms appear to be reversible when
exposure ceases. Considering the potential risk posed by UVB bulbs to reptiles and their
caretakers, a combination of broad■spectrum fluorescent bulbs and long■wavelength (UVA)
bulbs is probably the most practical starting point for husbandry of a species with unknown
requirements (Townsend and Cole, 1985). The bulbs should be as close as possible to the
tops of the cages, preferably within 15■20 cm of the animals. However, if symptoms of
vitamin D3 deficiency are observed, it may be wise to consider providing a source of UVB
radiation.
Because glass does not transmit middle■wavelength ultraviolet light and greatly
attenuates longer wavelengths, it should not be used for cage tops. Wire mesh and some
acrylic plastics and fluoroplastics transmit short■wavelength ultraviolet light and are suitable
for cage tops (Gehrmann, 1987).
The ultraviolet output of fluorescent bulbs decreases substantially after a few hundred
to a few thousand hours of use. Unfortunately, this change is not apparent to the human eye,
and can be easily overlooked until the animals' health is affected. Manufacturers can provide
information about the useful life of their bulbs, and a regular schedule of changing bulbs will
ensure that the animals are receiving ultraviolet light (Townsend and Cole, 1985).
The Biological Environment
Most amphibians and reptiles are secretive. They live in close association with their
structural microenvironments, and subtle cues--scent, texture, contact--are important aspects
of their behavior. Animals of this sort do not thrive in barren steel cages or in plastic boxes
filled with wood shavings; their husbandry requires housing that combines the animals' need
for environmental cues with effective care and sanitation. Providing hiding places is of
paramount importance for nearly all species.
Cage Furnishings. Cage and aquarium props (e.g., branches, rocks, and substrate) should
complement the normal lifestyle of the animal. A varied cage environment may be necessary
for normal behavior; for example, the thermoregulatory and foraging behaviors of Lacerta
vivipara break down in the absence of spatial diversity (Roger A. Avery, personal
communication). Many species of amphibians and reptiles require materials that duplicate
their natural settings for breeding. Terrestrial frogs such as Eleutherodactylus, Dendrobates,
and Colostethus breed in captivity when they are given suitable nest sites. In nature these
species deposit their eggs in smooth■surfaced fallen leaves, which should be included in the
cage. Nearly all animals require a hiding place; opaque plastic boxes with small entrance
holes make good retreat sites, and have the merit of being easily cleaned. Thigmotaxic
stimuli may be nearly as important as the darkness that opaque shelters provide. Cobras
used transparent plastic boxes as regularly as they used opaque boxes for hiding places when
the two kinds were tested sequentially. However, in simultaneous presentations, the snakes
always chose the opaque box (Chiszar et al., 1987). It can be advantageous to be able to see
an animal when it is in its retreat, and some situations may warrant the use of transparent
shelters.
Amphibians and reptiles often ingest bedding material with food, and cage substrates
should be chosen with this possibility in mind, and several substrates commonly used for bird
and mammal cages are harmful for amphibians and reptiles. Appropriate substrates keep the
animal dry, such as newspaper, indoor■outdoor carpet, sand (only for species that normally
live in sand), gravel (smooth particles that are fine enough to pass through the digestive
tract), crushed oyster shell (especially good for tortoises and large lizards and snakes),
hardwood mulch and bark chips, and peat and sphagnum moss. Materials that swell when
they are swallowed, such as ground corn cobs, kitty litter, the pine shavings used in rodent
cages, and cocoa shells, should not be used (Demeter, 1989). Cedar shavings have
neurotoxic properties and should not be used (Elliott Jacobson, personal communication).
Aspen shavings (Animal Bedding #2, American Excelsior Co., Arlington, TX) have proven
satisfactory for snakes (Ford, in press).
Many animals press their snouts against the walls of their cage as they explore, and
rough or sharp surfaces may injure them.
Behavioral Interactions. Many amphibians and reptiles are territorial in the field, and in
captivity often form dominance hierarchies. Initially the establishment of these
dominant■subordinate relationships is likely to involve fighting and the risk of injury,
especially because the loser is unable to leave the cage. After hierarchies have stabilized,
low■ranking individuals may be excluded from feeding, basking, or retreat sites (Regal,
1971). Aggressive behavior often waxes and wanes seasonally. For example, courtship can
lead to injury of a female that rejects a male's advances but is unable to escape from him.
Caretakers must be alert to subtle departures from normal behavior that indicate incipient
problems, as well as to the appearance of wounds and new scars.
Caretakers must also be aware of the sensory worlds of the animals and the stimuli
that are important to them. For example, it is stressful for a plethodontid salamander to be
moved into a cage that bears the scent of another individual, or to have pheromones from
another salamander deposited on its body during handling (Jaeger, in press). Ovarian
development of female lizards (Anolis carolinensis) has been reported to be accelerated by
the sight of male lizards giving courtship displays, and retarded by watching aggressive
interactions between males (Crews, 1975).
Social interactions may be important components of the biology of some amphibians
and reptiles. Crocodilians appear to be the most social reptiles, and parental care for young
after hatching is probably universal among crocodilians (Lang, 1987). Sibling groups of
young crocodilians remain with one or both parents for extended periods--as long as 24
months for the American alligator (Garrick and Lang, 1977; Hutton, 1989). Young
American alligators spend the day together, basking on land or moving back and forth
between land and water. At night the individuals disperse to forage, reassembling in the
morning (Deitz, 1979 (quoted in Lang, 1987)). Vocalizations by juveniles and adults assist
in maintaining these groups, and a distress call from a juvenile brings an adult to the rescue.
Juvenile and adult crocodilians may continue to associate in social groups, sometimes
segregated by age and sex. These social interactions have implications for management
(Lang, 1987), and the behavioral consequences of raising and maintaining crocodilians in
isolation have not been studied. The possibility that behavioral imprinting of juveniles occurs
during their association with their parents should be considered in husbandry programs.
Some lizards and snakes employ communal defecation, hiding, or egg■laying sites.
Several lizards and a few snakes remain with their eggs, and prolonged association between
mother and offspring has been reported for the Solomon Islands prehensile■tailed skink,
Corucia zebrata (John Groves, personal communication). Parental care by some species of
frogs extends to association between an adult and its tadpoles or hatchlings (see Duellman
and Trueb (1986) for examples). I suspect that social interactions are more widespread
among amphibians and reptiles than we currently realize, and in some cases may components
of successful husbandry.
Food. The type of food and the rate of feeding should, at a minimum, ensure normal
growth or maintenance of weight. (The nutritional requirements of breeding animals may be
different from those only being maintained.) The low metabolic rates and high conversion
efficiencies of ectotherms means that overfeeding of captive animals is more common than
underfeeding. The food requirements of amphibians and reptiles vary widely; some species
require nearly daily feeding, whereas others do best on three, two, or even one feeding per
week. Very large snakes may benefit from still longer intervals between meals. In general,
if a healthy animal that has adjusted to captivity does not accept food soon after it is offered,
the food should be removed and the animal allowed to fast until the next feeding time. In
salamanders, crocodilians, snakes, and lizards emaciation is first visible as concavity at the
base of the tail and prominence of the lateral processes of the caudal vertebrae. The pelvic
girdle of emaciated frogs is clearly outlined. While turtles exhibit fewer conspicuous signs
of emaciation, with experience it becomes easy to recognize a turtle that feels too light for its
size.
The foods that can be provided to amphibians and reptiles in captivity rarely resemble
their natural diets, and the nutritional requirements of amphibians and reptiles are poorly
understood. A varied diet is likely to be more nutritious and more readily accepted than a
diet consisting of only one kind of food. Providing balanced nutrition for amphibians and
reptiles is challenging, and a variety of opinions can be found in the literature. The
following paragraphs emphasize points of agreement, but the references should be consulted
for additional information and dissenting views.
Vitamins and Minerals. The routine use of supplementary vitamins and calcium is often
advised for amphibians and reptiles (Campbell and Busack, 1979; Allen et al., 1986; de
Vosjoli, 1990a; Staton et al., 1990), but generalizations about the quantities needed are
difficult to formulate. Studies of lizards have revealed substantial interspecific and
geographic variation in vitamin and mineral requirements, and the symptoms of vitamin
deficiency or excess are similarly variable (Larry Talent, personal communication). Many
multivitamin supplements don't state nutrient levels on their labels. Using a product without
knowing whether it has, for example, 5000 or 50,000 IU of vitamin A per gram is dangerous
(Mary Allen, personal communication).
As with UVB supplementation, we remain largely at a trial■and■error stage, and a
conservative approach to vitamin supplementation is probably the best starting point for a
species with unknown requirements. Selective supplementation of particular nutrients is
preferable to a shotgun approach. For example, a calcium:phosphorus ratio of 1.5:1
promotes normal bone growth.
Food items can be dusted with a vitamin■mineral mixture just before they are offered
to the animals; uneaten items should be removed from the cage. Most insects have low
levels of calcium, and dusting them with a calcium/phosoporous mixture that adjusts the ratio
is desirable. D■Ca■Fos■ (Fort Dodge Labs, Fort Dodge, IA 50501) is a finely powdered
mixture of vitamin D, calcium and phosphorus that can be applied to insects as small as fruit
flies and pinhead crickets. Beta■carotene and vitamins C and E may also be beneficial, but
excessive vitamin and mineral supplementation can cause problems (de Vosjoli 1990).
Feeding a balanced diet is preferable to supplementing an inadequate one.
The diets of anurans can be supplemented by putting slow■moving insects, such as
mealworms and wax moth larvae in shallow dishes with powdered vitamins and minerals.
When the frogs catch the insects, some of the powder adheres to their tongues and is
ingested with the prey. Many lizards will eat a mixture of dry vitamin and mineral powders
and fine silica sand from a dish (Larry Talent, personal communication).
Live Food. Many amphibians and reptiles respond to movement and will ignore even their
favorite prey if it is motionless. Live food is required for these animals, and husbandry of
amphibians and reptiles often requires maintaining colonies of insects as well.
Insects. Diets that alternate different kinds of live food are desirable, and a diet
consisting solely of mealworms is notoriously unsatisfactory (e.g., Demeter, 1989). A
combination of crickets (Acheta), mealworms (Tenebrio larvae), flour beetle larvae
(Tribolium) and wax moth (Galleria) or fly larvae (Sarcophaga) is suitable for insectivorous
lizards and amphibians. Roaches (Blaberus), king mealworms (Zoophobias), and fruit flies
(Drosophila) are also standard food items for captive amphibians and reptiles. The insects
must be healthy and well■fed if they are to be nutritious food. Insects that are not eaten
promptly should be removed from cages, because they may attack the animals. Suggested
diets and instructions for care of insects and other invertebrates are available in The
Encyclopedia of Live Foods (Masters, 1975), the Carolina Arthropods Manual (Anonymous,
1982), and The Right Way to Feed Insect■eating Lizards (de Vosjoli, 1990). Mary Allen
(National Zoo) recommends monkey chow and dog kibble as a stock cricket diet.
The material in the gut of insects is an important source of nutrients for amphibians
and reptiles, and insects can be nutrient■loaded to increase their food value. A high■calcium
diet for crickets (Cricket diet #39■390) is available from Ziegler Bros., Inc. (PO Box 95,
Gardners, PA 17325). This diet is intended for calcium■loading crickets before they are fed
to amphibians and reptiles; it is not suitable for rearing crickets. The gastrointestinal tracts
of crickets contained detectable quantities of calcium and phosphorus after 48 hours on the
high■calcium diet (see Allen and Oftedahl, 1989 for details and suggestions).
Birds and Mammals. Mice, rats, and hatchling chickens or quail should be
euthanized by an approved method that does not leave a toxic chemical residue before they
are fed to captive amphibians and reptiles. Asphyxiation with carbon dioxide or nitrogen is a
satisfactory method of killing animals for this purpose.
Prepared Diets. Although many amphibians and reptiles have narrow dietary preferences,
some species can be trained to accept prepared foods that incorporate vitamin and mineral
supplements. Good candidates for such dietary shifts are lizards and snakes that rely on
scent to identify food. Skinks (Eumeces, Chalcides, and many other genera), tegus and
dwarf tegus (Tupinambis and Callopistes), monitor lizards (Varanus), and natricine snakes
(Thamnophis, Nerodia, and related genera) will often learn to accept canned cat and dog
food. The odor of a fish■based food is sometimes particularly attractive, even to species that
never see a fish in their natural state. Dietary shifts can be facilitated by introducing them
gradually, a time■honored technique among reptile keepers (Weldon, in press). For
example, a lizard that eats mice can initially be given mice with progressively more cat food
spread on the fur, then cat food in a dish garnished with portions of a mouse carcass, and
finally plain cat food. Not all of the commercial foods for reptiles and amphibians that are
sold in pet stores provide a well■balanced diet, and advice about specific products should be
sought from a qualified source. Many of the major zoos now have nutritionists who can
provide helpful information.
Herbivorous Reptiles. Many species of reptiles include some plant material in their diets.
The most specialized of these are folivores (leaf■eaters). Prominent in this group are large
lizards (e.g., chuckwallas (Sauromalus), green iguanas (Iguana), ground iguanas (Cyclura),
the Galapagos marine and land iguanas (Amblyrhynchus and Conolophus), Fijian iguanas
(Brachylophus), mastigures (Uromastyx), the East Indian water lizard (Hydrosaurus), and the
green sea turtle (Chelonia mydas). These species rely on fermentative digestion and show
characteristic morphological and physiological specializations of the gut (Iverson, 1982;
McBee and McBee, 1982; Troyer, 1983, 1984a; Bjorndal, 1985; Bjorndal and Bolten, 1990).
Food particle size, the ratio of fruit to foliage, and the ratio of plant to animal material can
affect digestibility and the assimilation of energy and nutrients by herbivorous reptiles
(Bjorndal, 1989, 1991; Bjorndal et al. 1990).
Nutritionally complete diets for herbivorous reptiles are commercially available.
Ziegler Bros., Inc. (PO Box 95, Gardners, PA 17325) makes 15% and 25% crude protein
meal■type diets for iguanas, and a variation of that diet in small pellets for desert tortoises.
Marion Zoological (Marion, KS) makes an extruded diet of very small diameter for
herbivorous reptiles. A mixture of 10 parts by weight of leafy greens to one part soaked
dry dog food is a good alternative. The dog food should be soaked just enough to soften it
because excess water can leach out nutrients (Mary Allen, personal communication).
Chopped alfalfa hay is also accepted by tortoises, especially when it is mixed with greens.
The specializations of folivorous reptiles extend beyond morphology and physiology
to include behavior and ecology, and these phenomena must be considered in husbandry.
Like all folivores, reptiles are selective about the species and the parts of plants they eat.
Juvenile iguanas choose leaves with low fiber and high protein content, and they accelerate
digestion by maintaining body temperatures higher than those of adults (Troyer, 1984b,
1987). Social behavior probably also contributes to folivory for iguanas: newly hatched
green iguanas spend a short time in the tropical forest canopy where adult iguanas live before
returning to the forest■edge vegetation where they remain during their growth as juveniles.
Apparently this brief association of hatchlings with adults facilitates the transfer of the gut
symbionts responsible for fermentative digestion of plant matter (Troyer, 1982, 1984c).
Thus, juvenile folivores hatched in captivity and isolated from sources of normal symbionts
probably do not have their species' typical complement of fermentative microorganisms.
Although these individuals may grow and prosper on diets that do not require fermentation of
plant cell walls, their digestive physiology is probably not typical of free■ranging individuals.
This observation has important implications for laboratory studies that assume their subjects
to be in a normal physiological state, and for husbandry programs that rear juveniles for
release. In situations when digestive physiology is important, husbandry of folivorous
reptiles should probably include a method of inoculating hatchlings with the species' typical
gut symbionts. This may be a matter of substantial applied significance, because many
folivorous species of reptiles are threatened or endangered, and captive breeding programs
for some of them are planned or in progress (Bjorndal, 1981; Burghardt and Rand, 1982;
Miller, 1987; IUCN, 1989; Swingland and Klemens, 1989).
Housing and Sanitation. Housing conditions should inhibit the presence and spread of
disease. However, sanitation protocols should not frequently disturb the animals nor require
complete removal of feces because many ectothermal vertebrates use pheromones, including
constituents of feces, for intraspecific communication. Snakes kept in clean cages spend
more time attempting to escape than do individuals in cages where a small amount of fecal
matter is left each time the cage is cleaned (Chiszar et al., 1980). Similarly, plethodontid
salamanders mark their cages with pheromones in their feces, and salamanders in freshly
cleaned cages make more attempts to escape than do salamanders in cages they have marked
with their own scent (Jaeger, 1986 and references therein). Thus, excessive cleaning or
sterilization of cages can be deleterious to the well■being of the animals. The human nose is
the most appropriate guide to cleanliness: No odor of waste products should be perceptible in
the air of a room housing ectothermal animals. Application of this criterion is practical and
effective because unsanitary conditions are readily detected when the number of changes of
room air per hour is limited to maintain the high relative humidities amphibians and reptiles
require.
Through■flow aquatic systems are less likely to spread pathogens than are
recirculating systems. Chlorine should be removed from incoming water, which should be
heated or cooled to the appropriate temperature before it is introduced to the animals' tanks.
If a recirculating water system is necessary, each tank should have a self■contained system to
minimize the chances of cross■contamination. A sterilization process may be a desirable
component of recirculating aquatic systems.
Separate quarantine facilities are highly desirable for amphibians and reptiles, and
newly arrived animals should be kept in cages isolated from long■term stock for at least 90
days (Elliott Jacobson, personal communication). Checks for parasites should be routine.
These tests contribute to the health of the caretakers as well as to the welfare of the animals.
MARKING INDIVIDUALS
The ability to recognize individuals is critical to many studies, and methods of marking
amphibians and reptiles were reviewed by Ferner (1979). In many instances individual
variations in pattern allow even large numbers of animals to be distinguished without
artificial marks. When this is not possible, several techniques can be employed, depending
on whether long■term or short■term marks are needed. Clipping off portions of toes or
scales has traditionally been used to mark individuals, but toe clipping in particular is painful
and may affect locomotor ability, especially for arboreal species. Furthermore, some
individuals regenerate the clipped toes or lose additional toes in fights. Freeze■branding
appears to produce a mark that lasts one or two seasons. Passive integrated transponders
(PIT tags) have been used successfully to mark amphibians and reptiles, and this appears to
be the best method of permanently marking species that are large enough to accommodate the
tag (Camper and Dixon, 1988).
BREEDING
The reproductive cycles of amphibians and reptiles are closely linked to their physical and
biological environments, and effective breeding programs employ manipulation of these
factors (e.g, Crews and Garrick, 1980). Case■studies are published in the newsletters and
symposia of herpetological societies, the International Zoo Yearbook, and hobbyist literature.
As with most other aspects of herpetological husbandry, we are at the stage of trial and
error, and investigators should seek information about the species of interest to them from
those publications and from the staffs of zoos and aquaria, many of which have successful
breeding programs for several species. Some generalizations will provide a starting point,
for example, manipulating temperature, humidity, and photoperiod on an annual cycle has
been effective for many species. A period of one to four months of low temperature
stimulates breeding for a variety of reptiles and amphibians, including some tropical species.
This method has been applied successfully to snakes (e.g., Scheidt, 1984; Tryon and
Whitehead, 1988), as well as to lizards, turtles, and amphibians. Animals must be allowed
to fast before they are cooled, and a gradual reduction in temperature over a period of days
is preferable to an abrupt change. Environmental temperatures can be lowered to 10■C for
species from the temperate zone, whereas warmer temperatures (18■C■20■C) are appropriate
for tropical species. Most animals do not become torpid under these conditions, but emerge
from their hiding places during the day and retreat at night. A short photoperiod is more
natural than continuous darkness, and a daily temperature cycle may be desirable.
Dehydration is a risk in environmental chambers that regulate temperature by passing air
over refrigerating coils. The cages must prevent excessive water loss without allowing the
continuous contact with wet substrates which is likely to produce skin lesions. As the end of
the cool period approaches, the photoperiod should be lengthened and the temperature
gradually increased. Animals undergoing this treatment are not in any sense in cold storage
or suspended animation, and water dishes should be cleaned and refilled daily.
Seasons in some habitats, particularly in the tropics, are distinguished more clearly by
rainfall patterns than by temperature cycles. Animals from these habitats may be induced to
breed by simulated rain showers. This method was used by the Metropolitan Toronto Zoo to
breed Puerto Rican crested toads (Peltophryne lemur) (Paine et al., 1989). The breeding
schedule is keyed to environmental conditions in the toads■ natural habitat. In December,
which corresponds to the late part of the rainy season in Puerto Rico, feeding is increased,
and females receive newborn mice dusted with vitamin D3 and calcium supplements. In late
January, when the dry season is beginning, the toads are put into a cage that has been filled
with a water■soaked mixture of peat and sphagnum mosses. Ambient temperature is about
22■C, and the relative humidity is 50 to 70 percent. The toads burrow into the substrate,
which dries slowly during the next month; a shallow water dish in the cage allows the toads
to rehydrate when they emerge from the substrate at night. The toads are dug out of the
moss and fed weekly, until feeding ceases at about the time the moss dries completely. The
toads are kept for another month in the dry substrate, and checked regularly to see that they
remain hydrated.
At the end of 60 days of dryness, a time that corresponds to the usual onset of the
Puerto Rican rainy season, water is added gradually for two days until the moss is saturated
with water, and the air temperature is raised to 27■C. On the morning of the third day, the
males are transferred to tanks of water in which cultures of algae have been established. A
spray of water simulates rainfall, and tape recorded mating calls of the toads are played to
both sexes. The males are left in the breeding tanks for two days before the females are
added. The presence of a group of toads appears to contribute to the formation of amplexing
pairs, and amplexus normally begins very soon after the females are introduced. The
simulated rainfall and recordings of mating calls are continued for another three or four days.
The Toronto Zoo's program illustrates the effectiveness of techniques that initiate the
physiological changes associated with breeding by manipulating the physical and biological
conditions that stimulate breeding in nature. Another approach is to administer exogenous
hormones to initiate reproduction. This method has been widely used by embryologists to
induce breeding by amphibians (e.g., Rugh, 1962; National Academy of Sciences, 1974),
and the process is so simple that amphibian reproduction kits can be purchased from
biological supply houses. Pituitary glands from amphibians or human chorionic gonadotropin
have traditionally been employed for this purpose, but Goncharov et al. (1989) advocated the
use of synthetic analogues of luteinizing hormone■releasing hormone. Caution in the use of
these techniques may be desirable, because larvae produced by administration of exogenous
hormones might differ in morphology, growth rate, behavior, or viability from those
obtained from breedings that result from endogenous endocrine cycles. An extensive
literature of life■history studies testifies to the importance of maternal effects that are
controlled by environmental variables such as temperature and energy intake during
vitellogenesis (e.g., Kaplan, 1987). These interactions might be affected by interruption of
normal reproductive cycles, and if exogenous hormones are to be employed, their use should
be coordinated with the breeding cycle so that hormones are administered after gametes have
matured (Goncharov et al., 1989)
The nutritional status of a female reptile during oogenesis or pregnancy and the
environment in which eggs are reared can affect characters of the clutch and of the offspring.
In laboratory studies of viviparous and oviparous snakes the ratio of clutch mass (eggs or
embryos) to female body mass remained constant under different feeding regimes, with the
result that absolute reproductive effort (grams of offspring per female) was proportional to
energy intake (Ford and Siegel, 1989; 1991). That is, females that were well fed during
oogenesis produced larger litters than did females that received less food. In these
experiments, only the number of offspring responded to maternal nutritional status, but in
some species of reptiles the size and viability of the offspring might be affected. Viviparity
has evolved at least 45 times among lizards, and another 35 times among snakes (Blackburn,
1982, 1985). Modes of fetal nutrition among viviparous reptiles encompass a spectrum from
lecithotrophy (nutrients deposited in the yolk during vitellogenesis) to matrotrophy (nutrients
supplied throughout development via a placenta). The skink Mabuya heathi, a Brazilian
lizard, exhibits a nearly mammalian level of matrotrophy (Blackburn et al., 1984). The
newly ovulated egg is only 1 mm in diameter, and placental transport accounts for more than
99 percent of the dry mass of the fetus at birth. Another skink, Chalcides chalcides, a
species that is used in biological studies, may also rely primarily on matrotrophy during
embryonic development: the ova of C. chalcides are less than 3 mm in diameter at ovulation
(Blackburn et al., 1984). For these skinks, and for other reptiles with high levels of
maternal input to the fetus, the nutrition of a female during embryonic development may
influence the size and viability of the young she produces.
Temperature is an important factor in the embryonic development of reptiles. Normal
morphogenesis is limited to a narrow range of egg temperatures for some species of reptiles,
whereas others tolerate ranges as large as 10■C (Packard and Packard, 1988). Temperatures
outside those ranges may be lethal to the embryos, or may produce hatchlings with abnormal
skeletons, scale patterns, or pigmentation (Vinegar, 1973) as well as differences in
post■hatching survival (Whitehead et al., 1990). Snakes hatched from eggs that had been
incubated at intermediate temperatures performed better in several behavioral tests than
hatchlings from higher and lower incubation temperatures (Burger, 1989, 1990), and
alligators from eggs incubated at intermediate temperatures grew faster and survived better
than those from higher or lower temperatures (Joanen et al., 1987). Temperature■dependent
sex determination has been demonstrated for species in seven families of turtles, for
crocodilians, and for a few lizards (summarized by Paukstis and Janzen, 1990).
The wetness of the substrate on which reptile eggs are incubated affects the length of
the incubation period and the size and robustness of the hatchlings (Packard and Packard,
1988). The same phenomenon has been demonstrated for one species of frog (Taigen et al.,
1984). The largest and most vigorous turtle hatchlings are usually produced by incubating
eggs in wet substrates (water potentials of -100 to -200 kPa) at the lowest tolerable
temperatures (Gary C. Packard, personal communication). However, this advice must be
modified for species that display temperature■dependent sex determination to avoid producing
hatchlings of only one sex. As a rule of thumb, temperatures that produce incubation periods
similar to those observed in the field are likely to be satisfactory (Miller, 1987). Unlike the
eggs of birds, reptile eggs should not be turned during development.
ENVIRONMENTAL CONDITIONS AND MEDICAL CARE
A discussion of the veterinary requirements of amphibians and reptiles is beyond the scope of
this review, but the importance of environmental conditions, particularly temperature during
illness and following surgery should be noted. The role of temperature in reptilian health
management was reviewed by Mader (1985, 1991). Fishes, amphibians, and reptiles
maintain elevated body temperatures when they are injected with pathogens, and this
behavioral fever is associated with increased survival compared to animals that are prevented
from raising their temperatures (Vaughn et al., 1974; Kluger, 1977, 1979). The immune
response of reptiles is temperature■sensitive (Evans and Cowles, 1959; Evans, 1963; Cohen,
1971; Elkan, 1976), and antibiotic therapy also may be most effective at high temperatures
(Mader et al., 1985). Because behavioral fever is a normal response of reptiles and
amphibians to endogenous pyrogens, it may be desirable to allow the animals to control their
febrile response during antibiotic treatment and following surgery by keeping them in thermal
gradients so they can warm themselves several degrees above their normal activity
temperatures.
HEALTH PRECAUTIONS FOR RELEASE OF ANIMALS
The release of amphibians and reptiles that have been held in captivity is potentially
damaging to the health and the genetic composition of wild populations. It should be
prohibited in almost all cases. Cross■contamination of animals with pathogens is nearly
unavoidable in captivity, and amphibians and reptiles that are obtained from dealers have
been exposed to a wide range of microorganisms that they would not encounter in their
natural habitats. If these animals are released, the pathogens they carry can spread to the
wild population with potentially disastrous results. From 1987 to 1990 an outbreak of upper
respiratory distress syndrome (an infection by Pasturella testudinis and Mycoplasma spp)
reduced the population of desert tortoises at the Desert Tortoise Natural Area in California
from an estimated 1000 individuals 30 survivors. The outbreak may be associated, at least in
part, with the release of captive tortoises by well■meaning individuals (Elliott Jacobson,
personal communication).
Even in the absence of disease, the introduction of individuals from a distant part of a
species' range can change the genetic composition of local populations, and exotic species
may establish populations that compete with native species. A recent summary lists more
than 20 exotic species of reptiles and amphibians that have become established in the United
States (Conant and Collins, 1991).
Under some circumstances the release of animals does not pose a risk, or the risk can
be justified. If animals are rigorously isolated from any contact with other species while they
are in captivity and are returned to their sites of capture, no harm is likely to result. Work
with threatened or endangered species may require the release of animals after they have
been in captivity. In this case, the animals should be kept isolated from other species, and
from individuals of other populations of their own species, and they should be thoroughly
screened for parasites and pathogens before they are released. Institutional animal care and
use committees must be alert to the dangers associated with releasing animals. Committee
members must expand their view of animal welfare to consider impacts on wild, as well as
on captive populations. Unfortunately, the only possible option for animals that do not meet
the criteria for release may be euthanasia.
HEALTH PRECAUTIONS FOR ANIMAL CARETAKERS
Most amphibians and reptiles pose no greater risks for caretakers than do birds and
mammals. Normal precautions include washing the hands after working with the animals or
their feces. A dust mask should be worn when cages containing dry fecal material are
cleaned. Salmonella is frequently associated with reptiles, and its presence should be
assumed unless several cultures of fresh feces have given negative results.
Some amphibians have potent skin toxins, and a few species can be dangerous to
humans (e.g., Phyllobates terribilis; see Myers et al., 1978). Venomous snakes are
potentially dangerous to caretakers, as are the two species of venomous lizards (the gila
monster and Mexican beaded lizard, Heloderma suspectum and H. horridum). Dangerously
venomous snakes are not limited to vipers, elapids, and sea snakes; many colubrid snakes are
venomous and some of these can be dangerously toxic to an animal as large as a human.
Gans (1978, appendix 2) lists more than 40 species of venomous colubrids.
Husbandry of dangerously venomous snakes is a specialized activity involving legal
and ethical responsibilities that are beyond the scope of these general recommendations.
Most research programs do not require venomous snakes, and they should not be kept in an
academic institution without a compelling reason to do so. Gans and Taub (1978) discuss the
precautions that are necessary for housing venomous snakes, as well as the daunting legal
implications of keeping these potentially dangerous animals.
SUMMARY
Successful husbandry of amphibians and reptiles must be based on an understanding of the
ways in which they function as intact organisms. That is, one must know what physical and
biological factors are important to them, how they interact with their environments, and how
they exhibit signs of good or poor health. While the same principle applies to the care of a
laboratory mouse, amphibians and reptiles are sufficiently different from mammals that our
intuitive sense of what makes a suitable environment is not a satisfactory guide. Standards
based on mammalian husbandry likely to be detrimental to amphibians and reptiles. Intuition
must be replaced by an understanding of the unique characteristics of ectothermal vertebrates
and how these characteristics affect husbandry. Amphibians and reptiles are wild animals,
and we must adapt our laboratory techniques to their needs; we cannot expect them to adjust
their biology to suit our convenience.
ACKNOWLEDGEMENTS
Fred Quimby and Larry Carbone of the Center for Research Animal Resources at Cornell
University first encouraged me to prepare this review, and provided assistance in many
ways. I am grateful for their help, and for their commitment to providing the best possible
care for animals at Cornell. The topics covered here extend far beyond my personal
experience and rely on the contributions of colleagues at many institutions who read drafts of
the manuscript in various stages of its preparation, pointed out references, and provided
general information and specific details of their work. Mary Allen and B_la Demeter
(National Zoological Park), Robin Andrews (Virginia Polytechnic Institute and State
University), Roger Avery (University of Bristol), Cynthia Carey (University of Colorado),
Jay Cole (American Museum of Natural History), Lloyd Dillingham, Gabriel Foo, Jessica
Geyer, Neil Heinekamp, Paula Hintz, Barbara Lok, and Jennifer Weinheimer (Cornell
University), Katherine Graubard and Ellen Smith (University of Washington), Robin
Greenlee and Charles Radcliffe (San Diego Zoo), Neil Ford (University of Texas at Tyler),
William Gerhmann (Tarrant County Junior College), John Groves (Philadelphia Zoological
Garden), Elliott Jacobson (University of Florida), James Murphy (Dallas Zoo), Gary Packard
(Colorado State University), Larry Radford (Buffalo Zoo), Richard Shine (University of
Sydney),Larry Talent (Oklahoma State University), and Katherine Troyer (U. S. National
Museum of Natural History) generously shared their experience and opinions. The
development of techniques for husbandry of amphibians and reptiles in my laboratory has
been supported by a series of grants, including funding from NSF and NIH. The most
recent sources of support have been grants from the Hatch (Project NYC 183■412) and
McIntire Stennis (Project NYC183■572) programs.
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Figure Legends
Figure 1. Resting metabolic rates of terrestrial vertebrates as a function of body size.
Metabolic rates of salamanders are shown for 15■ and 25 ■C as the lower and upper
limits of the darkened area, and data for all reptiles are shown at 20■ and 30 ■C.
The metabolism■mass line for anurans falls within the "all reptiles" area, and the
relation for non■passerine birds is similar to that for placental mammals. Dotted
portions of the lines for birds and mammals show hypothetical extensions into body
sizes below the minimum sizes of most adult birds and mammals. From Pough
(1980), reprinted from The American Naturalist by permission of The University of
Chicago Press. ■ 1980 by The University of Chicago Press.
Figure 2. Adult body masses of amphibians and reptiles. The percentages of the total
number of taxa surveyed with body masses in the ranges <1, 1■5, 5■10, 10■20,
20■100, and > 100 g are shown. Sample sizes: salamanders, n = 198; anurans, n
= 1,330; caecilians, n = 160; snakes, n = 1,592; lizards, n = 1,780;
amphisbaenians, n = 110. From Pough (1983), reprinted by permission of the Ohio
State University Press.